The Truth (and Science) of Wine Preservation – Part 1

January 25, 2017

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It’s amazing how many wine “experts” don’t actually understand even the basic science of wine preservation.

Fine wine has always attracted more than its fair share of charlatans that take advantage of the high price points and mystique. The Internet is rife with a dangerous concoction of soft science and half-truths about wine preservation.

At Plum, we approached building a wine appliance like typical engineers: we wanted to understand the science behind it. If we were going to build a device that did a world-class job of preserving wine, we first needed to sift through the mountain of claims and theories to learn the facts about preservation. Here’s what we learned:

D.A.P.S: The Four Keys to Preservation

Most of the solid science on wine preservation is focused on the period of time from fermentation until bottling at the winery. This research is funded by wineries and their suppliers with the logical goal of ensuring their products are delivered to retailers and consumers as fresh as possible. Very little has actually been published about what happens after it goes in the bottle.

So our first goal was to figure out how you actually measure preservation of wine already in the bottle. Turns out, there are four things that really matter:

Dissolved Oxygen: Dissolved oxygen (DO) is the silent killer in wine preservation. The moment you remove a cork, oxygen in the atmosphere naturally dissolves into the wine until the wine is saturated. It will continue to oxidize a wine even if you add argon because the DO is already in the wine. Preventing DO (read: not pulling the cork) is crucial to any long-term preservation.

Acetaldehyde: You’ve probably heard the old adage that wine turns to vinegar. Turns out, this is not exactly true. As wine oxidizes, it actually turns into acetaldehyde (among other things), and only when you add heat as a catalyst, will it then turn into acetic acid, which is vinegar. Measuring acetaldehyde levels turns out to be extremely useful, as it is the proverbial canary in the coal mine. Acetaldehyde formation shows you that a wine is oxidizing. And in case you needed one more reason not to drink oxidized wine, acetaldehyde is also a Group 1 carcinogen.

Polyphenols: When you cut an apple open, it starts to quickly brown. This same thing happens in wine when tannins, the most common form of polyphenols, connect with oxygen. Tannins help a wine age, but when exposed to oxygen, they become polyphenol-oxidase. You can see this phenomenon in action when you pour an old bottle of Bordeaux and observe that deep reddish, brownish color. By performing rapid phenolic analysis on wine, you can see this change in color and determine the level of oxidation.

Sulfur Dioxide (SO2): SO2 is an additive used by wineries during winemaking and bottling to inhibit oxygen and prevent microbial growth. The moment you pull the cork, the free SO2 departs the bottle, and only SO2 that is bound to other molecules in the wine will remain. As SO2 levels drop, oxidation is increasing.

If you are going to make claims about preservation, it’s important to first understand how you are going to actually measure efficacy. Once we understood the science, we were able to design a much more effective method of preserving wine.

So what did we do about it?

In our next post, we’ll share how we translated what we learned to delivering industry-leading preservation with Plum.